A solar liquid heating installation is usually comprised of a storage tank and a solar collector. The system is generally filled with a liquid and a conduit leading liquid from the solar collector to the upper portion of the storage tank, as well as a conduit returning liquid from the storage tank to the solar collector. With the absorption of sun rays by the solar collector, a natural or motoric circulation is created between the storage tank and the solar collector.
In the prevalent type of such installations, the larger the internal volume of the storage tank, the more time it takes to heat the liquid in the storage tank. The solar collectors, which provide heat to the storage tank, are subject to the heating of all the liquid in the storage tank. That means that a hot liquid of desired temperature from the storage tank is not obtainable until all the liquid in the storage tank has reached that temperature. This disadvantage is especially present with relatively large storage tanks, since one must wait a long time, in order to utilize the respective liquid--mostly hot water.